1. Field of the Disclosure
This disclosure relates to a laser and specifically to a solid state or fiber laser that generates radiation near 193 nm and is suitable for use in inspection of photomasks, reticles, and/or wafers. The laser may be pulsed (Q-switched or mode-locked) or CW (continuous wave).
2. Related Art
Excimer lasers for generating light at 193 nm are well known in the art. Unfortunately, such lasers are not well suited to inspection applications because of their low laser pulse repetition rates and their use of toxic and corrosive gases in their lasing medium, which leads to high cost of ownership.
Solid state and fiber lasers for generating light near 193 nm are also known. Exemplary lasers use two different fundamental wavelengths or the eighth harmonic of the fundamental, either of which requires lasers or materials that are expensive or are not in high volume production. Moreover, most of these lasers have very low power output and are limited to laser pulse repetition rates of a few MHz or less.
Therefore, a need arises for a laser and preferably to a solid state or fiber laser that generates radiation near 193 nm and is suitable for use in inspection of photomasks, reticles, and/or wafers. Notably, such inspections at high speeds often require minimum laser pulse repetition rates of multiple MHz (e.g. greater than 50 MHz in some cases).